Not applicable.
1. The Field of the Invention
The invention is in the field of dental bonding compositions, more particularly temporary dental cements used to temporarily bond a dental prosthesis to a person""s tooth.
2. The Relevant Technology
Permanent dental cements are employed to adhere a dental appliance or prosthesis to a tooth which has been prepared to receive the prosthesis or appliance. Permanent dental cements typically comprise two parts, with one part comprising a glass ionomer silica and a second part comprising a polyacrylic acid. Mixing together the glass ionomer silica and aqueous polyacrylic acid results in an acid-base reaction that yields a salt. The salt has a matrix which forms a strong bond between the tooth and a prosthesis or appliance.
When resins are employed as a permanent bonding material, such as luting cements for crowns, the deposition of the final permanent bonding material is typically preceded by the application of a hydrophilic resin primer to the tooth preparation. Bonding primers bond to the tooth surface, after which the permanent resin-based luting cement is bonded onto the bonding primer. The use of a bonding primer increases the overall adhesion of the luting cement to the tooth.
Although permanent dental cements are highly useful for a variety of different dental purposes where a permanent bond is desired, it may be desirable in some cases to temporarily affix a prosthesis or appliance to a tooth, then later remove the prosthesis or appliance. For example, before mounting a permanent crown on a tooth which has been prepared to receive the crown, a dentist typically makes an impression of the tooth. The dentist then mounts a temporary crown on the tooth and sends the impression to a laboratory for manufacture of the permanent crown.
The temporary crown is held in place by a temporary dental cement until the permanent crown is prepared. Thereafter, the temporary crown is removed. The permanent crown is then permanently affixed to the tooth through the use of a permanent dental cement. One type of temporary dental cement comprises eugenol, rosin, pine gum, or tall oil mixed with zinc oxide. One problem with such dental cements is that they are hydrophobic. Because of this, such temporary cements are not able to form a chemical seal both with and against the tooth. Forming a poor seal can lead to tooth sensitivity and infection.
Another problem is that such temporary dental cements are hard to remove completely. They can leave an insoluble, oily residue on a tooth and/or contaminate the underlying dentin and/or enamel so as to inhibit or prevent the later formation of a permanent bond after removal of the temporary cement. This oily residue can be difficult to remove, particularly by rinsing with water or through the use of conventional drying agents used in the dental art. The oily residues do not bond well to hydrophilic primers and can even inhibit polymerization of hydrophobic resins. Thus, temporary cements that contain eugenol or other hydrophobic oils or resins must generally be cleaned off with another hydrophobic composition, such as oil of orange, or another hydrophobic cleaner. Furthermore, typical hydrophobic temporary cements, such as eugenol, can also be irritating to nerve and pulp tissues. For these and other reasons, temporary bonding cements comprising eugenol or other hydrophobic oils or resins have become highly disfavored by many dental practitioners.
In view of the foregoing problems inherent in eugenol-based or other hydrophobic temporary dental cements, some have proposed the use of more hydrophilic temporary dental cements. The theory behind using a hydrophilic temporary cement is that hydrophilic materials are more chemically compatible with dental tissues and, as such, would be expected to form a better bond and seal against a patient""s tooth. In addition, temporary bonding cements that are hydrophilic would be expected to be more easily washed off using water or mixtures of water and hydrophilic solvents.
Nevertheless, whereas hydrophilic temporary bonding cements have solved some problems associated with hydrophobic temporary cements, they have created other problems. For example, U.S. Pat. No. 6,306,206 to Fischer et al., discloses a temporary dental cement that is similar to permanent dental cements in that it employs a two-part system involving an ion leaching agent and a polyacrylic acid, but that has been modified so as to include a sugar or sugar-derivative in order to form a more temporary bond that can be more easily removed at a later time. For purposes of disclosing temporary dental compositions and methods of preparing and using such compositions, the foregoing patent is incorporated by reference. One drawback of such compositions, or even permanent dental cements based on similar chemistry, is that they can cause significant pain to the patient when first applied. As a result, it is recommended that such compositions only be used on patients under anesthesia.
In view of the foregoing, there is a need to provide temporary dental cements that are able to form a good bond and seal against the tooth but which do not cause significant pain when applied to a patient""s tooth. This is especially true in the case where a patient or other person needs to temporarily fix a tooth, such as a filling or crown that has become dislodged, or to temporarily repair a painful cavity or a tooth that has been broken at a time when it is inconvenient or impossible to visit a dentist.
Improved temporary dental cements and methods for temporarily repairing a person""s tooth with reduced sensitivity are disclosed and claimed herein.
The present invention relates to temporary dental cements having reduced tooth sensitivity when placed against a person""s tooth. The invention also relates to kits and methods that utilize such compositions. The inventive compositions can be used by dental practitioners when attaching a temporary prosthesis to a patient""s tooth, as well as by persons who need to temporarily repair a broken or dislodged dental prosthesis or tooth defect outside the context of a visit to a dental practitioner.
Such temporary dental cements can be sold over-the-counter in order to allow a person to repair his or her own tooth without the immediate assistance of a dental practitioner. This may occur, for example, when a person is traveling or is in a remote location and cannot immediately visit a dentist. Or the person may have an emergency that arises at night, over the weekend or during some other time frame when it is inconvenient or impossible to visit a dentist. The inventive compositions may, of course, be used by a dental practitioner to temporarily bond a dental prosthesis to a patient""s tooth with reduced pain or sensitivity.
The temporary dental cements according to the invention comprise an acid in one component and a base in another component which, when mixed together in the presence of water, react to form a curable material that is capable of bonding to a person""s tooth. The acid component is typically a polycarboxylic acid (e.g., polyacrylic acid) that is hydrophilic. The base component is typically a metal oxide (e.g., zinc oxide) or other ion leaching agent that reacts with the acid component.
The two components are mixed together prior to application, which causes them to undergo an acid-based reaction so as to form a metal carboxylate polymer that is able to adhere to teeth. The metal carboxylate polymer can also serve as a cement so as to bond a temporary prosthetic to a person""s teeth, or it may be used to simply fill a void within a person""s teeth. However, at least one of the acid or the reaction between the acid and base components is believed to be responsible for causing tooth sensitivity or irritation.
In order to ameliorate or at least partially reduce the pain caused by the reaction of the acid and base components, the temporary dental cements according to the invention include one or more soothing agents that are able to greatly reduce or eliminate tooth sensitivity. The soothing agent typically comprises a hydrophobic oil. However, because the soothing oils typically constitute a relatively small fraction of the overall composition, they do not hinder the ability of the metal carboxylate polymer to form a good seal against a tooth surface. The relatively low concentration of the hydrophobic soothing oil yields a temporary bonding cement that is still sufficiently hydrophilic that it can be easily removed from the tooth without leaving behind an oily film, as typically occurs using conventional hydrophobic temporary bonding cements.
Examples of soothing agents that may be used within the scope of the invention include 2-ethoxybenzoic acid, 2-methoxy-4-methylphenol, eugenol, rosin, pine gum, tall oil, and the like.
The compositions according to the invention may also include a sugar or sugar-derivative (e.g., sorbitol) in order to form a temporary dental cement that can be more easily removed when needed preparatory to applying a permanent bonding cement to the person""s tooth. The sugar or sugar-derivative may also help emulsify and/or suspend non-water soluble components within aqueous components or compositions prior to mixing them together.
Thickening agents, such as precipitated silicon dioxide, fumed silica, fumed aluminum oxide, colloidal silica, and the like may be used to increase the viscosity of the bonding compositions and form a composition having a desired consistency. The thickening agents may also impart thixotropy to the compositions in some cases to yield a composition that can be easily expressed or manipulated into a crack or crevice of a patient""s tooth but which will not easily run off but remain in place while curing.
The temporary dental cements according to the invention typically comprise a multi-part composition in which the acid component is contained in one part and the base component is contained in another part. The parts may be solutions, suspensions, colloids, or a mixture of dry ingredients as desired. One or more soothing agents, the thickening agent, and other desired components may be contained in one or both of the acid and base parts. One or both of the acid and base components may include water, although it is certainly within the scope of the invention to provide one or both of the acid and base components as dry mixtures that are later mixed with water when it is desired to form the temporary dental cement. For example, water can be provided separately from the acid and base components if desired.
The temporary dental cements according to the invention may be included within a kit that also contains one or more additional components that facilitate the temporary repair process. For example, the kits may include a stirring device such as a metal, wooden or plastic rod, spatula, spoon and the like or other mixing devices known in the art. The kits may also include an application device, such as a spatula or a specially adapted syringe (e.g., multi-barrel syringe) and syringe tip suitable for placing the temporary dental cement onto a tooth in the desired location. The initially unmixed components can be preloaded into syringes, squeeze tubes or other appropriate dispensing devices. The kits may also include other compositions, such as an anesthetic composition that can be applied to a painful tooth to provide temporary anesthesia, a drying agent, a priming agent, and the like.
When it is desired to temporarily repair a broken or dislodged dental filling, prosthesis or appliance (hereinafter collectively referred to as xe2x80x9cdental prosthesisxe2x80x9d), the dental prosthesis may be removed or adjusted so as to allow the application of the temporary dental cement onto the tooth, followed by placement of the dental prosthesis. It is also within the scope of the invention to use the temporary dental cement to simply fill or seal a crack, crevice or other defect within a person""s tooth to reduce pain until professional dental treatment can be obtained.
Because the temporary bonding cements according to the invention are hydrophilic, they can be easily removed prepatory to applying a permanent bonding agent or dental cement to the person""s tooth. The temporary dental cements according to the present invention may be cleaned off as needed using water-based scouring agents, such as CONSEPSIS SCRUB, which is available from Ultradent Products, Inc., located in South Jordan, Utah.
These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.